CONCERNED parents should be forewarned: The surface of hundreds of plastic toys designed for young children contains a hidden danger — harmful chemicals called phthalates.

California has banned these chemicals for use in children's toys. The federal government should do the same.

Some doubt whether phthalates actually pose a serious danger to children. Evidence continues to mount that these exposures can be dangerous. Let me describe the risks:

Phthalates are added to plastic products to make them soft and pliable. They are widely used in products that often wind up young children's mouths — rubber ducks, teething rings and soft bath books. They are also found in common household items like vinyl shower curtains, paint, and nail polish.

The danger is this: When a child places a plastic toy into his or her mouth, these harmful chemicals leach out of the plastic and into the system — and exposure to phthalates can cause serious long-term health effects, such as reproductive defects.

Here's what we should do: Ban toys and child care products that have more than a trace amount (0.1 percent) of any one of six types of phthalates and require manufactures to use a safe alternative.

The European Union has a complete ban, and Mexico has blocked imports and sales of products for children. Thirteen additional countries have taken steps to ban or restrict their use.

We cannot allow the United States to become a dumping ground for toys that can no longer be legally sold elsewhere.

The full dangers remain unknown, but we already know that these chemicals interfere with the functioning of the hormone system, and can cause reproductive abnormalities.

For example:

  • Pregnant women with high levels in their bodies are more likely to give birth to boys with birth defects in their reproductive system.

  • Men with high levels have lower sperm counts and damaged sperm DNA.

  • Phthalate exposure has also been linked to premature birth and the early onset of puberty, which may be a factor in some cancers.

In 2005, a study by the Centers for Disease Control found elevated levels of phthalates in children's bodies.

The science is clear: phthalates pose a serious risk to children.

Yet today, they are often used in dangerous levels in many items designed for child use.

In a 2006 study, a Chicago lab tested phthalate levels in 16 children's toys.

The results were alarming:

  • One teething ring contained a phthalate chemical five times greater than trace levels (0.1 percent).

  • One rubber duck was found to have a carcinogenic phthalate at 13 times greater than trace levels.

  • The plastic face of a popular doll was found to have phthalates levels greater than twice trace amounts.

So, the danger is real.

Some say that there are not adequate alternatives, but this is not true.

European manufacturers have found ways to make safe, phthalate-free toys without harming their bottom line. One Danish company has introduced an alternative that has been approved for use in toys in both the United States and the European Union.

There is absolutely no reason that manufacturers should not do the same for American children.

Bottom line: It's time to give America's parents the peace of mind that the toys in the hands of their children are safe.

Dianne Feinstein is the senior U.S. senator for California.